1 /*-
2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 1994 John S. Dyson
5 * All rights reserved.
6 * Copyright (c) 1994 David Greenman
7 * All rights reserved.
8 *
9 *
10 * This code is derived from software contributed to Berkeley by
11 * The Mach Operating System project at Carnegie-Mellon University.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. All advertising materials mentioning features or use of this software
22 * must display the following acknowledgement:
23 * This product includes software developed by the University of
24 * California, Berkeley and its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * SUCH DAMAGE.
40 *
41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94
42 *
43 *
44 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
45 * All rights reserved.
46 *
47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
48 *
49 * Permission to use, copy, modify and distribute this software and
50 * its documentation is hereby granted, provided that both the copyright
51 * notice and this permission notice appear in all copies of the
52 * software, derivative works or modified versions, and any portions
53 * thereof, and that both notices appear in supporting documentation.
54 *
55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
58 *
59 * Carnegie Mellon requests users of this software to return to
60 *
61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
62 * School of Computer Science
63 * Carnegie Mellon University
64 * Pittsburgh PA 15213-3890
65 *
66 * any improvements or extensions that they make and grant Carnegie the
67 * rights to redistribute these changes.
68 */
69
70 /*
71 * Page fault handling module.
72 */
73
74 #include <sys/cdefs.h>
75 __FBSDID("$FreeBSD$");
76
77 #include "opt_ktrace.h"
78 #include "opt_vm.h"
79
80 #include <sys/param.h>
81 #include <sys/systm.h>
82 #include <sys/kernel.h>
83 #include <sys/lock.h>
84 #include <sys/mman.h>
85 #include <sys/proc.h>
86 #include <sys/resourcevar.h>
87 #include <sys/rwlock.h>
88 #include <sys/sysctl.h>
89 #include <sys/vmmeter.h>
90 #include <sys/vnode.h>
91 #ifdef KTRACE
92 #include <sys/ktrace.h>
93 #endif
94
95 #include <vm/vm.h>
96 #include <vm/vm_param.h>
97 #include <vm/pmap.h>
98 #include <vm/vm_map.h>
99 #include <vm/vm_object.h>
100 #include <vm/vm_page.h>
101 #include <vm/vm_pageout.h>
102 #include <vm/vm_kern.h>
103 #include <vm/vm_pager.h>
104 #include <vm/vm_extern.h>
105 #include <vm/vm_reserv.h>
106
107 #define PFBAK 4
108 #define PFFOR 4
109
110 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT)
111 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX)
112
113 #define VM_FAULT_DONTNEED_MIN 1048576
114
115 struct faultstate {
116 vm_page_t m;
117 vm_object_t object;
118 vm_pindex_t pindex;
119 vm_page_t first_m;
120 vm_object_t first_object;
121 vm_pindex_t first_pindex;
122 vm_map_t map;
123 vm_map_entry_t entry;
124 int lookup_still_valid;
125 struct vnode *vp;
126 };
127
128 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
129 int ahead);
130 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
131 int backward, int forward);
132
133 static inline void
release_page(struct faultstate * fs)134 release_page(struct faultstate *fs)
135 {
136
137 vm_page_xunbusy(fs->m);
138 vm_page_lock(fs->m);
139 vm_page_deactivate(fs->m);
140 vm_page_unlock(fs->m);
141 fs->m = NULL;
142 }
143
144 static inline void
unlock_map(struct faultstate * fs)145 unlock_map(struct faultstate *fs)
146 {
147
148 if (fs->lookup_still_valid) {
149 vm_map_lookup_done(fs->map, fs->entry);
150 fs->lookup_still_valid = FALSE;
151 }
152 }
153
154 static void
unlock_and_deallocate(struct faultstate * fs)155 unlock_and_deallocate(struct faultstate *fs)
156 {
157
158 vm_object_pip_wakeup(fs->object);
159 VM_OBJECT_WUNLOCK(fs->object);
160 if (fs->object != fs->first_object) {
161 VM_OBJECT_WLOCK(fs->first_object);
162 vm_page_lock(fs->first_m);
163 vm_page_free(fs->first_m);
164 vm_page_unlock(fs->first_m);
165 vm_object_pip_wakeup(fs->first_object);
166 VM_OBJECT_WUNLOCK(fs->first_object);
167 fs->first_m = NULL;
168 }
169 vm_object_deallocate(fs->first_object);
170 unlock_map(fs);
171 if (fs->vp != NULL) {
172 vput(fs->vp);
173 fs->vp = NULL;
174 }
175 }
176
177 static void
vm_fault_dirty(vm_map_entry_t entry,vm_page_t m,vm_prot_t prot,vm_prot_t fault_type,int fault_flags,boolean_t set_wd)178 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
179 vm_prot_t fault_type, int fault_flags, boolean_t set_wd)
180 {
181 boolean_t need_dirty;
182
183 if (((prot & VM_PROT_WRITE) == 0 &&
184 (fault_flags & VM_FAULT_DIRTY) == 0) ||
185 (m->oflags & VPO_UNMANAGED) != 0)
186 return;
187
188 VM_OBJECT_ASSERT_LOCKED(m->object);
189
190 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
191 (fault_flags & VM_FAULT_WIRE) == 0) ||
192 (fault_flags & VM_FAULT_DIRTY) != 0;
193
194 if (set_wd)
195 vm_object_set_writeable_dirty(m->object);
196 else
197 /*
198 * If two callers of vm_fault_dirty() with set_wd ==
199 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
200 * flag set, other with flag clear, race, it is
201 * possible for the no-NOSYNC thread to see m->dirty
202 * != 0 and not clear VPO_NOSYNC. Take vm_page lock
203 * around manipulation of VPO_NOSYNC and
204 * vm_page_dirty() call, to avoid the race and keep
205 * m->oflags consistent.
206 */
207 vm_page_lock(m);
208
209 /*
210 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
211 * if the page is already dirty to prevent data written with
212 * the expectation of being synced from not being synced.
213 * Likewise if this entry does not request NOSYNC then make
214 * sure the page isn't marked NOSYNC. Applications sharing
215 * data should use the same flags to avoid ping ponging.
216 */
217 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
218 if (m->dirty == 0) {
219 m->oflags |= VPO_NOSYNC;
220 }
221 } else {
222 m->oflags &= ~VPO_NOSYNC;
223 }
224
225 /*
226 * If the fault is a write, we know that this page is being
227 * written NOW so dirty it explicitly to save on
228 * pmap_is_modified() calls later.
229 *
230 * Also tell the backing pager, if any, that it should remove
231 * any swap backing since the page is now dirty.
232 */
233 if (need_dirty)
234 vm_page_dirty(m);
235 if (!set_wd)
236 vm_page_unlock(m);
237 if (need_dirty)
238 vm_pager_page_unswapped(m);
239 }
240
241 /*
242 * vm_fault:
243 *
244 * Handle a page fault occurring at the given address,
245 * requiring the given permissions, in the map specified.
246 * If successful, the page is inserted into the
247 * associated physical map.
248 *
249 * NOTE: the given address should be truncated to the
250 * proper page address.
251 *
252 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
253 * a standard error specifying why the fault is fatal is returned.
254 *
255 * The map in question must be referenced, and remains so.
256 * Caller may hold no locks.
257 */
258 int
vm_fault(vm_map_t map,vm_offset_t vaddr,vm_prot_t fault_type,int fault_flags)259 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
260 int fault_flags)
261 {
262 struct thread *td;
263 int result;
264
265 td = curthread;
266 if ((td->td_pflags & TDP_NOFAULTING) != 0)
267 return (KERN_PROTECTION_FAILURE);
268 #ifdef KTRACE
269 if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
270 ktrfault(vaddr, fault_type);
271 #endif
272 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
273 NULL);
274 #ifdef KTRACE
275 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
276 ktrfaultend(result);
277 #endif
278 return (result);
279 }
280
281 int
vm_fault_hold(vm_map_t map,vm_offset_t vaddr,vm_prot_t fault_type,int fault_flags,vm_page_t * m_hold)282 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
283 int fault_flags, vm_page_t *m_hold)
284 {
285 vm_prot_t prot;
286 int alloc_req, era, faultcount, nera, result;
287 boolean_t growstack, is_first_object_locked, wired;
288 int map_generation;
289 vm_object_t next_object;
290 int hardfault;
291 struct faultstate fs;
292 struct vnode *vp;
293 vm_page_t m;
294 int ahead, behind, cluster_offset, error, locked;
295
296 hardfault = 0;
297 growstack = TRUE;
298 PCPU_INC(cnt.v_vm_faults);
299 fs.vp = NULL;
300 faultcount = 0;
301
302 RetryFault:;
303
304 /*
305 * Find the backing store object and offset into it to begin the
306 * search.
307 */
308 fs.map = map;
309 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
310 &fs.first_object, &fs.first_pindex, &prot, &wired);
311 if (result != KERN_SUCCESS) {
312 if (growstack && result == KERN_INVALID_ADDRESS &&
313 map != kernel_map) {
314 result = vm_map_growstack(curproc, vaddr);
315 if (result != KERN_SUCCESS)
316 return (KERN_FAILURE);
317 growstack = FALSE;
318 goto RetryFault;
319 }
320 return (result);
321 }
322
323 map_generation = fs.map->timestamp;
324
325 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
326 panic("vm_fault: fault on nofault entry, addr: %lx",
327 (u_long)vaddr);
328 }
329
330 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
331 fs.entry->wiring_thread != curthread) {
332 vm_map_unlock_read(fs.map);
333 vm_map_lock(fs.map);
334 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
335 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
336 if (fs.vp != NULL) {
337 vput(fs.vp);
338 fs.vp = NULL;
339 }
340 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
341 vm_map_unlock_and_wait(fs.map, 0);
342 } else
343 vm_map_unlock(fs.map);
344 goto RetryFault;
345 }
346
347 if (wired)
348 fault_type = prot | (fault_type & VM_PROT_COPY);
349 else
350 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
351 ("!wired && VM_FAULT_WIRE"));
352
353 if (fs.vp == NULL /* avoid locked vnode leak */ &&
354 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
355 /* avoid calling vm_object_set_writeable_dirty() */
356 ((prot & VM_PROT_WRITE) == 0 ||
357 (fs.first_object->type != OBJT_VNODE &&
358 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
359 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
360 VM_OBJECT_RLOCK(fs.first_object);
361 if ((prot & VM_PROT_WRITE) != 0 &&
362 (fs.first_object->type == OBJT_VNODE ||
363 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) &&
364 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0)
365 goto fast_failed;
366 m = vm_page_lookup(fs.first_object, fs.first_pindex);
367 /* A busy page can be mapped for read|execute access. */
368 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
369 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
370 goto fast_failed;
371 result = pmap_enter(fs.map->pmap, vaddr, m, prot,
372 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED :
373 0), 0);
374 if (result != KERN_SUCCESS)
375 goto fast_failed;
376 if (m_hold != NULL) {
377 *m_hold = m;
378 vm_page_lock(m);
379 vm_page_hold(m);
380 vm_page_unlock(m);
381 }
382 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags,
383 FALSE);
384 VM_OBJECT_RUNLOCK(fs.first_object);
385 if (!wired)
386 vm_fault_prefault(&fs, vaddr, PFBAK, PFFOR);
387 vm_map_lookup_done(fs.map, fs.entry);
388 curthread->td_ru.ru_minflt++;
389 return (KERN_SUCCESS);
390 fast_failed:
391 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
392 VM_OBJECT_RUNLOCK(fs.first_object);
393 VM_OBJECT_WLOCK(fs.first_object);
394 }
395 } else {
396 VM_OBJECT_WLOCK(fs.first_object);
397 }
398
399 /*
400 * Make a reference to this object to prevent its disposal while we
401 * are messing with it. Once we have the reference, the map is free
402 * to be diddled. Since objects reference their shadows (and copies),
403 * they will stay around as well.
404 *
405 * Bump the paging-in-progress count to prevent size changes (e.g.
406 * truncation operations) during I/O. This must be done after
407 * obtaining the vnode lock in order to avoid possible deadlocks.
408 */
409 vm_object_reference_locked(fs.first_object);
410 vm_object_pip_add(fs.first_object, 1);
411
412 fs.lookup_still_valid = TRUE;
413
414 fs.first_m = NULL;
415
416 /*
417 * Search for the page at object/offset.
418 */
419 fs.object = fs.first_object;
420 fs.pindex = fs.first_pindex;
421 while (TRUE) {
422 /*
423 * If the object is dead, we stop here
424 */
425 if (fs.object->flags & OBJ_DEAD) {
426 unlock_and_deallocate(&fs);
427 return (KERN_PROTECTION_FAILURE);
428 }
429
430 /*
431 * See if page is resident
432 */
433 fs.m = vm_page_lookup(fs.object, fs.pindex);
434 if (fs.m != NULL) {
435 /*
436 * Wait/Retry if the page is busy. We have to do this
437 * if the page is either exclusive or shared busy
438 * because the vm_pager may be using read busy for
439 * pageouts (and even pageins if it is the vnode
440 * pager), and we could end up trying to pagein and
441 * pageout the same page simultaneously.
442 *
443 * We can theoretically allow the busy case on a read
444 * fault if the page is marked valid, but since such
445 * pages are typically already pmap'd, putting that
446 * special case in might be more effort then it is
447 * worth. We cannot under any circumstances mess
448 * around with a shared busied page except, perhaps,
449 * to pmap it.
450 */
451 if (vm_page_busied(fs.m)) {
452 /*
453 * Reference the page before unlocking and
454 * sleeping so that the page daemon is less
455 * likely to reclaim it.
456 */
457 vm_page_aflag_set(fs.m, PGA_REFERENCED);
458 if (fs.object != fs.first_object) {
459 if (!VM_OBJECT_TRYWLOCK(
460 fs.first_object)) {
461 VM_OBJECT_WUNLOCK(fs.object);
462 VM_OBJECT_WLOCK(fs.first_object);
463 VM_OBJECT_WLOCK(fs.object);
464 }
465 vm_page_lock(fs.first_m);
466 vm_page_free(fs.first_m);
467 vm_page_unlock(fs.first_m);
468 vm_object_pip_wakeup(fs.first_object);
469 VM_OBJECT_WUNLOCK(fs.first_object);
470 fs.first_m = NULL;
471 }
472 unlock_map(&fs);
473 if (fs.m == vm_page_lookup(fs.object,
474 fs.pindex)) {
475 vm_page_sleep_if_busy(fs.m, "vmpfw");
476 }
477 vm_object_pip_wakeup(fs.object);
478 VM_OBJECT_WUNLOCK(fs.object);
479 PCPU_INC(cnt.v_intrans);
480 vm_object_deallocate(fs.first_object);
481 goto RetryFault;
482 }
483 vm_page_lock(fs.m);
484 vm_page_remque(fs.m);
485 vm_page_unlock(fs.m);
486
487 /*
488 * Mark page busy for other processes, and the
489 * pagedaemon. If it still isn't completely valid
490 * (readable), jump to readrest, else break-out ( we
491 * found the page ).
492 */
493 vm_page_xbusy(fs.m);
494 if (fs.m->valid != VM_PAGE_BITS_ALL)
495 goto readrest;
496 break;
497 }
498
499 /*
500 * Page is not resident. If this is the search termination
501 * or the pager might contain the page, allocate a new page.
502 * Default objects are zero-fill, there is no real pager.
503 */
504 if (fs.object->type != OBJT_DEFAULT ||
505 fs.object == fs.first_object) {
506 if (fs.pindex >= fs.object->size) {
507 unlock_and_deallocate(&fs);
508 return (KERN_PROTECTION_FAILURE);
509 }
510
511 /*
512 * Allocate a new page for this object/offset pair.
513 *
514 * Unlocked read of the p_flag is harmless. At
515 * worst, the P_KILLED might be not observed
516 * there, and allocation can fail, causing
517 * restart and new reading of the p_flag.
518 */
519 fs.m = NULL;
520 if (!vm_page_count_severe() || P_KILLED(curproc)) {
521 #if VM_NRESERVLEVEL > 0
522 vm_object_color(fs.object, atop(vaddr) -
523 fs.pindex);
524 #endif
525 alloc_req = P_KILLED(curproc) ?
526 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
527 if (fs.object->type != OBJT_VNODE &&
528 fs.object->backing_object == NULL)
529 alloc_req |= VM_ALLOC_ZERO;
530 fs.m = vm_page_alloc(fs.object, fs.pindex,
531 alloc_req);
532 }
533 if (fs.m == NULL) {
534 unlock_and_deallocate(&fs);
535 VM_WAITPFAULT;
536 goto RetryFault;
537 } else if (fs.m->valid == VM_PAGE_BITS_ALL)
538 break;
539 }
540
541 readrest:
542 /*
543 * We have found a valid page or we have allocated a new page.
544 * The page thus may not be valid or may not be entirely
545 * valid.
546 *
547 * Attempt to fault-in the page if there is a chance that the
548 * pager has it, and potentially fault in additional pages
549 * at the same time. For default objects simply provide
550 * zero-filled pages.
551 */
552 if (fs.object->type != OBJT_DEFAULT) {
553 int rv;
554 u_char behavior = vm_map_entry_behavior(fs.entry);
555
556 era = fs.entry->read_ahead;
557 if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
558 P_KILLED(curproc)) {
559 behind = 0;
560 nera = 0;
561 ahead = 0;
562 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
563 behind = 0;
564 nera = VM_FAULT_READ_AHEAD_MAX;
565 ahead = nera;
566 if (fs.pindex == fs.entry->next_read)
567 vm_fault_dontneed(&fs, vaddr, ahead);
568 } else if (fs.pindex == fs.entry->next_read) {
569 /*
570 * This is a sequential fault. Arithmetically
571 * increase the requested number of pages in
572 * the read-ahead window. The requested
573 * number of pages is "# of sequential faults
574 * x (read ahead min + 1) + read ahead min"
575 */
576 behind = 0;
577 nera = VM_FAULT_READ_AHEAD_MIN;
578 if (era > 0) {
579 nera += era + 1;
580 if (nera > VM_FAULT_READ_AHEAD_MAX)
581 nera = VM_FAULT_READ_AHEAD_MAX;
582 }
583 ahead = nera;
584 if (era == VM_FAULT_READ_AHEAD_MAX)
585 vm_fault_dontneed(&fs, vaddr, ahead);
586 } else {
587 /*
588 * This is a non-sequential fault. Request a
589 * cluster of pages that is aligned to a
590 * VM_FAULT_READ_DEFAULT page offset boundary
591 * within the object. Alignment to a page
592 * offset boundary is more likely to coincide
593 * with the underlying file system block than
594 * alignment to a virtual address boundary.
595 */
596 cluster_offset = fs.pindex %
597 VM_FAULT_READ_DEFAULT;
598 behind = ulmin(cluster_offset,
599 atop(vaddr - fs.entry->start));
600 nera = 0;
601 ahead = VM_FAULT_READ_DEFAULT - 1 -
602 cluster_offset;
603 }
604 ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1);
605 if (era != nera)
606 fs.entry->read_ahead = nera;
607
608 /*
609 * Call the pager to retrieve the data, if any, after
610 * releasing the lock on the map. We hold a ref on
611 * fs.object and the pages are exclusive busied.
612 */
613 unlock_map(&fs);
614
615 if (fs.object->type == OBJT_VNODE) {
616 vp = fs.object->handle;
617 if (vp == fs.vp)
618 goto vnode_locked;
619 else if (fs.vp != NULL) {
620 vput(fs.vp);
621 fs.vp = NULL;
622 }
623 locked = VOP_ISLOCKED(vp);
624
625 if (locked != LK_EXCLUSIVE)
626 locked = LK_SHARED;
627 /* Do not sleep for vnode lock while fs.m is busy */
628 error = vget(vp, locked | LK_CANRECURSE |
629 LK_NOWAIT, curthread);
630 if (error != 0) {
631 vhold(vp);
632 release_page(&fs);
633 unlock_and_deallocate(&fs);
634 error = vget(vp, locked | LK_RETRY |
635 LK_CANRECURSE, curthread);
636 vdrop(vp);
637 fs.vp = vp;
638 KASSERT(error == 0,
639 ("vm_fault: vget failed"));
640 goto RetryFault;
641 }
642 fs.vp = vp;
643 }
644 vnode_locked:
645 KASSERT(fs.vp == NULL || !fs.map->system_map,
646 ("vm_fault: vnode-backed object mapped by system map"));
647
648 /*
649 * Page in the requested page and hint the pager,
650 * that it may bring up surrounding pages.
651 */
652 rv = vm_pager_get_pages(fs.object, &fs.m, 1,
653 &behind, &ahead);
654 if (rv == VM_PAGER_OK) {
655 faultcount = behind + 1 + ahead;
656 hardfault++;
657 break; /* break to PAGE HAS BEEN FOUND */
658 }
659 /*
660 * Remove the bogus page (which does not exist at this
661 * object/offset); before doing so, we must get back
662 * our object lock to preserve our invariant.
663 *
664 * Also wake up any other process that may want to bring
665 * in this page.
666 *
667 * If this is the top-level object, we must leave the
668 * busy page to prevent another process from rushing
669 * past us, and inserting the page in that object at
670 * the same time that we are.
671 */
672 if (rv == VM_PAGER_ERROR)
673 printf("vm_fault: pager read error, pid %d (%s)\n",
674 curproc->p_pid, curproc->p_comm);
675 /*
676 * Data outside the range of the pager or an I/O error
677 */
678 /*
679 * XXX - the check for kernel_map is a kludge to work
680 * around having the machine panic on a kernel space
681 * fault w/ I/O error.
682 */
683 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
684 (rv == VM_PAGER_BAD)) {
685 vm_page_lock(fs.m);
686 vm_page_free(fs.m);
687 vm_page_unlock(fs.m);
688 fs.m = NULL;
689 unlock_and_deallocate(&fs);
690 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
691 }
692 if (fs.object != fs.first_object) {
693 vm_page_lock(fs.m);
694 vm_page_free(fs.m);
695 vm_page_unlock(fs.m);
696 fs.m = NULL;
697 /*
698 * XXX - we cannot just fall out at this
699 * point, m has been freed and is invalid!
700 */
701 }
702 }
703
704 /*
705 * We get here if the object has default pager (or unwiring)
706 * or the pager doesn't have the page.
707 */
708 if (fs.object == fs.first_object)
709 fs.first_m = fs.m;
710
711 /*
712 * Move on to the next object. Lock the next object before
713 * unlocking the current one.
714 */
715 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
716 next_object = fs.object->backing_object;
717 if (next_object == NULL) {
718 /*
719 * If there's no object left, fill the page in the top
720 * object with zeros.
721 */
722 if (fs.object != fs.first_object) {
723 vm_object_pip_wakeup(fs.object);
724 VM_OBJECT_WUNLOCK(fs.object);
725
726 fs.object = fs.first_object;
727 fs.pindex = fs.first_pindex;
728 fs.m = fs.first_m;
729 VM_OBJECT_WLOCK(fs.object);
730 }
731 fs.first_m = NULL;
732
733 /*
734 * Zero the page if necessary and mark it valid.
735 */
736 if ((fs.m->flags & PG_ZERO) == 0) {
737 pmap_zero_page(fs.m);
738 } else {
739 PCPU_INC(cnt.v_ozfod);
740 }
741 PCPU_INC(cnt.v_zfod);
742 fs.m->valid = VM_PAGE_BITS_ALL;
743 /* Don't try to prefault neighboring pages. */
744 faultcount = 1;
745 break; /* break to PAGE HAS BEEN FOUND */
746 } else {
747 KASSERT(fs.object != next_object,
748 ("object loop %p", next_object));
749 VM_OBJECT_WLOCK(next_object);
750 vm_object_pip_add(next_object, 1);
751 if (fs.object != fs.first_object)
752 vm_object_pip_wakeup(fs.object);
753 VM_OBJECT_WUNLOCK(fs.object);
754 fs.object = next_object;
755 }
756 }
757
758 vm_page_assert_xbusied(fs.m);
759
760 /*
761 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
762 * is held.]
763 */
764
765 /*
766 * If the page is being written, but isn't already owned by the
767 * top-level object, we have to copy it into a new page owned by the
768 * top-level object.
769 */
770 if (fs.object != fs.first_object) {
771 /*
772 * We only really need to copy if we want to write it.
773 */
774 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
775 /*
776 * This allows pages to be virtually copied from a
777 * backing_object into the first_object, where the
778 * backing object has no other refs to it, and cannot
779 * gain any more refs. Instead of a bcopy, we just
780 * move the page from the backing object to the
781 * first object. Note that we must mark the page
782 * dirty in the first object so that it will go out
783 * to swap when needed.
784 */
785 is_first_object_locked = FALSE;
786 if (
787 /*
788 * Only one shadow object
789 */
790 (fs.object->shadow_count == 1) &&
791 /*
792 * No COW refs, except us
793 */
794 (fs.object->ref_count == 1) &&
795 /*
796 * No one else can look this object up
797 */
798 (fs.object->handle == NULL) &&
799 /*
800 * No other ways to look the object up
801 */
802 ((fs.object->type == OBJT_DEFAULT) ||
803 (fs.object->type == OBJT_SWAP)) &&
804 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
805 /*
806 * We don't chase down the shadow chain
807 */
808 fs.object == fs.first_object->backing_object) {
809 /*
810 * get rid of the unnecessary page
811 */
812 vm_page_lock(fs.first_m);
813 vm_page_remove(fs.first_m);
814 vm_page_unlock(fs.first_m);
815 /*
816 * grab the page and put it into the
817 * process'es object. The page is
818 * automatically made dirty.
819 */
820 if (vm_page_rename(fs.m, fs.first_object,
821 fs.first_pindex)) {
822 VM_OBJECT_WUNLOCK(fs.first_object);
823 unlock_and_deallocate(&fs);
824 goto RetryFault;
825 }
826 vm_page_lock(fs.first_m);
827 vm_page_free(fs.first_m);
828 vm_page_unlock(fs.first_m);
829 #if VM_NRESERVLEVEL > 0
830 /*
831 * Rename the reservation.
832 */
833 vm_reserv_rename(fs.m, fs.first_object,
834 fs.object, OFF_TO_IDX(
835 fs.first_object->backing_object_offset));
836 #endif
837 vm_page_xbusy(fs.m);
838 fs.first_m = fs.m;
839 fs.m = NULL;
840 PCPU_INC(cnt.v_cow_optim);
841 } else {
842 /*
843 * Oh, well, lets copy it.
844 */
845 pmap_copy_page(fs.m, fs.first_m);
846 fs.first_m->valid = VM_PAGE_BITS_ALL;
847 if (wired && (fault_flags &
848 VM_FAULT_WIRE) == 0) {
849 vm_page_lock(fs.first_m);
850 vm_page_wire(fs.first_m);
851 vm_page_unlock(fs.first_m);
852
853 vm_page_lock(fs.m);
854 vm_page_unwire(fs.m, PQ_INACTIVE);
855 vm_page_unlock(fs.m);
856 }
857 /*
858 * We no longer need the old page or object.
859 */
860 release_page(&fs);
861 }
862 /*
863 * fs.object != fs.first_object due to above
864 * conditional
865 */
866 vm_object_pip_wakeup(fs.object);
867 VM_OBJECT_WUNLOCK(fs.object);
868 /*
869 * Only use the new page below...
870 */
871 fs.object = fs.first_object;
872 fs.pindex = fs.first_pindex;
873 fs.m = fs.first_m;
874 if (!is_first_object_locked)
875 VM_OBJECT_WLOCK(fs.object);
876 PCPU_INC(cnt.v_cow_faults);
877 curthread->td_cow++;
878 } else {
879 prot &= ~VM_PROT_WRITE;
880 }
881 }
882
883 /*
884 * We must verify that the maps have not changed since our last
885 * lookup.
886 */
887 if (!fs.lookup_still_valid) {
888 vm_object_t retry_object;
889 vm_pindex_t retry_pindex;
890 vm_prot_t retry_prot;
891
892 if (!vm_map_trylock_read(fs.map)) {
893 release_page(&fs);
894 unlock_and_deallocate(&fs);
895 goto RetryFault;
896 }
897 fs.lookup_still_valid = TRUE;
898 if (fs.map->timestamp != map_generation) {
899 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
900 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
901
902 /*
903 * If we don't need the page any longer, put it on the inactive
904 * list (the easiest thing to do here). If no one needs it,
905 * pageout will grab it eventually.
906 */
907 if (result != KERN_SUCCESS) {
908 release_page(&fs);
909 unlock_and_deallocate(&fs);
910
911 /*
912 * If retry of map lookup would have blocked then
913 * retry fault from start.
914 */
915 if (result == KERN_FAILURE)
916 goto RetryFault;
917 return (result);
918 }
919 if ((retry_object != fs.first_object) ||
920 (retry_pindex != fs.first_pindex)) {
921 release_page(&fs);
922 unlock_and_deallocate(&fs);
923 goto RetryFault;
924 }
925
926 /*
927 * Check whether the protection has changed or the object has
928 * been copied while we left the map unlocked. Changing from
929 * read to write permission is OK - we leave the page
930 * write-protected, and catch the write fault. Changing from
931 * write to read permission means that we can't mark the page
932 * write-enabled after all.
933 */
934 prot &= retry_prot;
935 }
936 }
937 /*
938 * If the page was filled by a pager, update the map entry's
939 * last read offset.
940 *
941 * XXX The following assignment modifies the map
942 * without holding a write lock on it.
943 */
944 if (hardfault)
945 fs.entry->next_read = fs.pindex + ahead + 1;
946
947 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE);
948 vm_page_assert_xbusied(fs.m);
949
950 /*
951 * Page must be completely valid or it is not fit to
952 * map into user space. vm_pager_get_pages() ensures this.
953 */
954 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
955 ("vm_fault: page %p partially invalid", fs.m));
956 VM_OBJECT_WUNLOCK(fs.object);
957
958 /*
959 * Put this page into the physical map. We had to do the unlock above
960 * because pmap_enter() may sleep. We don't put the page
961 * back on the active queue until later so that the pageout daemon
962 * won't find it (yet).
963 */
964 pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
965 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
966 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
967 wired == 0)
968 vm_fault_prefault(&fs, vaddr,
969 faultcount > 0 ? behind : PFBAK,
970 faultcount > 0 ? ahead : PFFOR);
971 VM_OBJECT_WLOCK(fs.object);
972 vm_page_lock(fs.m);
973
974 /*
975 * If the page is not wired down, then put it where the pageout daemon
976 * can find it.
977 */
978 if ((fault_flags & VM_FAULT_WIRE) != 0) {
979 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
980 vm_page_wire(fs.m);
981 } else
982 vm_page_activate(fs.m);
983 if (m_hold != NULL) {
984 *m_hold = fs.m;
985 vm_page_hold(fs.m);
986 }
987 vm_page_unlock(fs.m);
988 vm_page_xunbusy(fs.m);
989
990 /*
991 * Unlock everything, and return
992 */
993 unlock_and_deallocate(&fs);
994 if (hardfault) {
995 PCPU_INC(cnt.v_io_faults);
996 curthread->td_ru.ru_majflt++;
997 } else
998 curthread->td_ru.ru_minflt++;
999
1000 return (KERN_SUCCESS);
1001 }
1002
1003 /*
1004 * Speed up the reclamation of pages that precede the faulting pindex within
1005 * the first object of the shadow chain. Essentially, perform the equivalent
1006 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1007 * the faulting pindex by the cluster size when the pages read by vm_fault()
1008 * cross a cluster-size boundary. The cluster size is the greater of the
1009 * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1010 *
1011 * When "fs->first_object" is a shadow object, the pages in the backing object
1012 * that precede the faulting pindex are deactivated by vm_fault(). So, this
1013 * function must only be concerned with pages in the first object.
1014 */
1015 static void
vm_fault_dontneed(const struct faultstate * fs,vm_offset_t vaddr,int ahead)1016 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1017 {
1018 vm_map_entry_t entry;
1019 vm_object_t first_object, object;
1020 vm_offset_t end, start;
1021 vm_page_t m, m_next;
1022 vm_pindex_t pend, pstart;
1023 vm_size_t size;
1024
1025 object = fs->object;
1026 VM_OBJECT_ASSERT_WLOCKED(object);
1027 first_object = fs->first_object;
1028 if (first_object != object) {
1029 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1030 VM_OBJECT_WUNLOCK(object);
1031 VM_OBJECT_WLOCK(first_object);
1032 VM_OBJECT_WLOCK(object);
1033 }
1034 }
1035 /* Neither fictitious nor unmanaged pages can be reclaimed. */
1036 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1037 size = VM_FAULT_DONTNEED_MIN;
1038 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1039 size = pagesizes[1];
1040 end = rounddown2(vaddr, size);
1041 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1042 (entry = fs->entry)->start < end) {
1043 if (end - entry->start < size)
1044 start = entry->start;
1045 else
1046 start = end - size;
1047 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1048 pstart = OFF_TO_IDX(entry->offset) + atop(start -
1049 entry->start);
1050 m_next = vm_page_find_least(first_object, pstart);
1051 pend = OFF_TO_IDX(entry->offset) + atop(end -
1052 entry->start);
1053 while ((m = m_next) != NULL && m->pindex < pend) {
1054 m_next = TAILQ_NEXT(m, listq);
1055 if (m->valid != VM_PAGE_BITS_ALL ||
1056 vm_page_busied(m))
1057 continue;
1058
1059 /*
1060 * Don't clear PGA_REFERENCED, since it would
1061 * likely represent a reference by a different
1062 * process.
1063 *
1064 * Typically, at this point, prefetched pages
1065 * are still in the inactive queue. Only
1066 * pages that triggered page faults are in the
1067 * active queue.
1068 */
1069 vm_page_lock(m);
1070 vm_page_deactivate(m);
1071 vm_page_unlock(m);
1072 }
1073 }
1074 }
1075 if (first_object != object)
1076 VM_OBJECT_WUNLOCK(first_object);
1077 }
1078
1079 /*
1080 * vm_fault_prefault provides a quick way of clustering
1081 * pagefaults into a processes address space. It is a "cousin"
1082 * of vm_map_pmap_enter, except it runs at page fault time instead
1083 * of mmap time.
1084 */
1085 static void
vm_fault_prefault(const struct faultstate * fs,vm_offset_t addra,int backward,int forward)1086 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1087 int backward, int forward)
1088 {
1089 pmap_t pmap;
1090 vm_map_entry_t entry;
1091 vm_object_t backing_object, lobject;
1092 vm_offset_t addr, starta;
1093 vm_pindex_t pindex;
1094 vm_page_t m;
1095 int i;
1096
1097 pmap = fs->map->pmap;
1098 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1099 return;
1100
1101 entry = fs->entry;
1102
1103 starta = addra - backward * PAGE_SIZE;
1104 if (starta < entry->start) {
1105 starta = entry->start;
1106 } else if (starta > addra) {
1107 starta = 0;
1108 }
1109
1110 /*
1111 * Generate the sequence of virtual addresses that are candidates for
1112 * prefaulting in an outward spiral from the faulting virtual address,
1113 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1114 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1115 * If the candidate address doesn't have a backing physical page, then
1116 * the loop immediately terminates.
1117 */
1118 for (i = 0; i < 2 * imax(backward, forward); i++) {
1119 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1120 PAGE_SIZE);
1121 if (addr > addra + forward * PAGE_SIZE)
1122 addr = 0;
1123
1124 if (addr < starta || addr >= entry->end)
1125 continue;
1126
1127 if (!pmap_is_prefaultable(pmap, addr))
1128 continue;
1129
1130 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1131 lobject = entry->object.vm_object;
1132 VM_OBJECT_RLOCK(lobject);
1133 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1134 lobject->type == OBJT_DEFAULT &&
1135 (backing_object = lobject->backing_object) != NULL) {
1136 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1137 0, ("vm_fault_prefault: unaligned object offset"));
1138 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1139 VM_OBJECT_RLOCK(backing_object);
1140 VM_OBJECT_RUNLOCK(lobject);
1141 lobject = backing_object;
1142 }
1143 if (m == NULL) {
1144 VM_OBJECT_RUNLOCK(lobject);
1145 break;
1146 }
1147 if (m->valid == VM_PAGE_BITS_ALL &&
1148 (m->flags & PG_FICTITIOUS) == 0)
1149 pmap_enter_quick(pmap, addr, m, entry->protection);
1150 VM_OBJECT_RUNLOCK(lobject);
1151 }
1152 }
1153
1154 /*
1155 * Hold each of the physical pages that are mapped by the specified range of
1156 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1157 * and allow the specified types of access, "prot". If all of the implied
1158 * pages are successfully held, then the number of held pages is returned
1159 * together with pointers to those pages in the array "ma". However, if any
1160 * of the pages cannot be held, -1 is returned.
1161 */
1162 int
vm_fault_quick_hold_pages(vm_map_t map,vm_offset_t addr,vm_size_t len,vm_prot_t prot,vm_page_t * ma,int max_count)1163 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1164 vm_prot_t prot, vm_page_t *ma, int max_count)
1165 {
1166 vm_offset_t end, va;
1167 vm_page_t *mp;
1168 int count;
1169 boolean_t pmap_failed;
1170
1171 if (len == 0)
1172 return (0);
1173 end = round_page(addr + len);
1174 addr = trunc_page(addr);
1175
1176 /*
1177 * Check for illegal addresses.
1178 */
1179 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1180 return (-1);
1181
1182 if (atop(end - addr) > max_count)
1183 panic("vm_fault_quick_hold_pages: count > max_count");
1184 count = atop(end - addr);
1185
1186 /*
1187 * Most likely, the physical pages are resident in the pmap, so it is
1188 * faster to try pmap_extract_and_hold() first.
1189 */
1190 pmap_failed = FALSE;
1191 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1192 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1193 if (*mp == NULL)
1194 pmap_failed = TRUE;
1195 else if ((prot & VM_PROT_WRITE) != 0 &&
1196 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1197 /*
1198 * Explicitly dirty the physical page. Otherwise, the
1199 * caller's changes may go unnoticed because they are
1200 * performed through an unmanaged mapping or by a DMA
1201 * operation.
1202 *
1203 * The object lock is not held here.
1204 * See vm_page_clear_dirty_mask().
1205 */
1206 vm_page_dirty(*mp);
1207 }
1208 }
1209 if (pmap_failed) {
1210 /*
1211 * One or more pages could not be held by the pmap. Either no
1212 * page was mapped at the specified virtual address or that
1213 * mapping had insufficient permissions. Attempt to fault in
1214 * and hold these pages.
1215 */
1216 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1217 if (*mp == NULL && vm_fault_hold(map, va, prot,
1218 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1219 goto error;
1220 }
1221 return (count);
1222 error:
1223 for (mp = ma; mp < ma + count; mp++)
1224 if (*mp != NULL) {
1225 vm_page_lock(*mp);
1226 vm_page_unhold(*mp);
1227 vm_page_unlock(*mp);
1228 }
1229 return (-1);
1230 }
1231
1232 /*
1233 * Routine:
1234 * vm_fault_copy_entry
1235 * Function:
1236 * Create new shadow object backing dst_entry with private copy of
1237 * all underlying pages. When src_entry is equal to dst_entry,
1238 * function implements COW for wired-down map entry. Otherwise,
1239 * it forks wired entry into dst_map.
1240 *
1241 * In/out conditions:
1242 * The source and destination maps must be locked for write.
1243 * The source map entry must be wired down (or be a sharing map
1244 * entry corresponding to a main map entry that is wired down).
1245 */
1246 void
vm_fault_copy_entry(vm_map_t dst_map,vm_map_t src_map,vm_map_entry_t dst_entry,vm_map_entry_t src_entry,vm_ooffset_t * fork_charge)1247 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1248 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1249 vm_ooffset_t *fork_charge)
1250 {
1251 vm_object_t backing_object, dst_object, object, src_object;
1252 vm_pindex_t dst_pindex, pindex, src_pindex;
1253 vm_prot_t access, prot;
1254 vm_offset_t vaddr;
1255 vm_page_t dst_m;
1256 vm_page_t src_m;
1257 boolean_t upgrade;
1258
1259 #ifdef lint
1260 src_map++;
1261 #endif /* lint */
1262
1263 upgrade = src_entry == dst_entry;
1264 access = prot = dst_entry->protection;
1265
1266 src_object = src_entry->object.vm_object;
1267 src_pindex = OFF_TO_IDX(src_entry->offset);
1268
1269 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1270 dst_object = src_object;
1271 vm_object_reference(dst_object);
1272 } else {
1273 /*
1274 * Create the top-level object for the destination entry. (Doesn't
1275 * actually shadow anything - we copy the pages directly.)
1276 */
1277 dst_object = vm_object_allocate(OBJT_DEFAULT,
1278 OFF_TO_IDX(dst_entry->end - dst_entry->start));
1279 #if VM_NRESERVLEVEL > 0
1280 dst_object->flags |= OBJ_COLORED;
1281 dst_object->pg_color = atop(dst_entry->start);
1282 #endif
1283 }
1284
1285 VM_OBJECT_WLOCK(dst_object);
1286 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1287 ("vm_fault_copy_entry: vm_object not NULL"));
1288 if (src_object != dst_object) {
1289 dst_entry->object.vm_object = dst_object;
1290 dst_entry->offset = 0;
1291 dst_object->charge = dst_entry->end - dst_entry->start;
1292 }
1293 if (fork_charge != NULL) {
1294 KASSERT(dst_entry->cred == NULL,
1295 ("vm_fault_copy_entry: leaked swp charge"));
1296 dst_object->cred = curthread->td_ucred;
1297 crhold(dst_object->cred);
1298 *fork_charge += dst_object->charge;
1299 } else if (dst_object->cred == NULL) {
1300 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1301 dst_entry));
1302 dst_object->cred = dst_entry->cred;
1303 dst_entry->cred = NULL;
1304 }
1305
1306 /*
1307 * If not an upgrade, then enter the mappings in the pmap as
1308 * read and/or execute accesses. Otherwise, enter them as
1309 * write accesses.
1310 *
1311 * A writeable large page mapping is only created if all of
1312 * the constituent small page mappings are modified. Marking
1313 * PTEs as modified on inception allows promotion to happen
1314 * without taking potentially large number of soft faults.
1315 */
1316 if (!upgrade)
1317 access &= ~VM_PROT_WRITE;
1318
1319 /*
1320 * Loop through all of the virtual pages within the entry's
1321 * range, copying each page from the source object to the
1322 * destination object. Since the source is wired, those pages
1323 * must exist. In contrast, the destination is pageable.
1324 * Since the destination object does share any backing storage
1325 * with the source object, all of its pages must be dirtied,
1326 * regardless of whether they can be written.
1327 */
1328 for (vaddr = dst_entry->start, dst_pindex = 0;
1329 vaddr < dst_entry->end;
1330 vaddr += PAGE_SIZE, dst_pindex++) {
1331 again:
1332 /*
1333 * Find the page in the source object, and copy it in.
1334 * Because the source is wired down, the page will be
1335 * in memory.
1336 */
1337 if (src_object != dst_object)
1338 VM_OBJECT_RLOCK(src_object);
1339 object = src_object;
1340 pindex = src_pindex + dst_pindex;
1341 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1342 (backing_object = object->backing_object) != NULL) {
1343 /*
1344 * Unless the source mapping is read-only or
1345 * it is presently being upgraded from
1346 * read-only, the first object in the shadow
1347 * chain should provide all of the pages. In
1348 * other words, this loop body should never be
1349 * executed when the source mapping is already
1350 * read/write.
1351 */
1352 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1353 upgrade,
1354 ("vm_fault_copy_entry: main object missing page"));
1355
1356 VM_OBJECT_RLOCK(backing_object);
1357 pindex += OFF_TO_IDX(object->backing_object_offset);
1358 if (object != dst_object)
1359 VM_OBJECT_RUNLOCK(object);
1360 object = backing_object;
1361 }
1362 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1363
1364 if (object != dst_object) {
1365 /*
1366 * Allocate a page in the destination object.
1367 */
1368 dst_m = vm_page_alloc(dst_object, (src_object ==
1369 dst_object ? src_pindex : 0) + dst_pindex,
1370 VM_ALLOC_NORMAL);
1371 if (dst_m == NULL) {
1372 VM_OBJECT_WUNLOCK(dst_object);
1373 VM_OBJECT_RUNLOCK(object);
1374 VM_WAIT;
1375 VM_OBJECT_WLOCK(dst_object);
1376 goto again;
1377 }
1378 pmap_copy_page(src_m, dst_m);
1379 VM_OBJECT_RUNLOCK(object);
1380 dst_m->valid = VM_PAGE_BITS_ALL;
1381 dst_m->dirty = VM_PAGE_BITS_ALL;
1382 } else {
1383 dst_m = src_m;
1384 if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1385 goto again;
1386 vm_page_xbusy(dst_m);
1387 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1388 ("invalid dst page %p", dst_m));
1389 }
1390 VM_OBJECT_WUNLOCK(dst_object);
1391
1392 /*
1393 * Enter it in the pmap. If a wired, copy-on-write
1394 * mapping is being replaced by a write-enabled
1395 * mapping, then wire that new mapping.
1396 */
1397 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1398 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1399
1400 /*
1401 * Mark it no longer busy, and put it on the active list.
1402 */
1403 VM_OBJECT_WLOCK(dst_object);
1404
1405 if (upgrade) {
1406 if (src_m != dst_m) {
1407 vm_page_lock(src_m);
1408 vm_page_unwire(src_m, PQ_INACTIVE);
1409 vm_page_unlock(src_m);
1410 vm_page_lock(dst_m);
1411 vm_page_wire(dst_m);
1412 vm_page_unlock(dst_m);
1413 } else {
1414 KASSERT(dst_m->wire_count > 0,
1415 ("dst_m %p is not wired", dst_m));
1416 }
1417 } else {
1418 vm_page_lock(dst_m);
1419 vm_page_activate(dst_m);
1420 vm_page_unlock(dst_m);
1421 }
1422 vm_page_xunbusy(dst_m);
1423 }
1424 VM_OBJECT_WUNLOCK(dst_object);
1425 if (upgrade) {
1426 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1427 vm_object_deallocate(src_object);
1428 }
1429 }
1430
1431 /*
1432 * Block entry into the machine-independent layer's page fault handler by
1433 * the calling thread. Subsequent calls to vm_fault() by that thread will
1434 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
1435 * spurious page faults.
1436 */
1437 int
vm_fault_disable_pagefaults(void)1438 vm_fault_disable_pagefaults(void)
1439 {
1440
1441 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1442 }
1443
1444 void
vm_fault_enable_pagefaults(int save)1445 vm_fault_enable_pagefaults(int save)
1446 {
1447
1448 curthread_pflags_restore(save);
1449 }
1450